1. Technical Field
Example embodiments of the present invention relate in general to a technology for cancelling interference in a wireless communication system, and more specifically, to a method of cancelling inter-subcarrier interference in a wireless communication system, which can efficiently cancel inter-subcarrier interference in a frequency selective fading channel environment, and an apparatus for the same.
2. Related Art
According to rapid advances of wireless communication system, demands on transmitting and receiving a high-speed large amount of data are increasing. For this, a method of installing a plurality of distributed antennas additionally in the conventional cell coverage, and performing cooperative communications between a plurality of transmitters and a plurality of receivers, which are geographically distributed, is being used.
Such the distributed antenna system has an effect of resolving a problem of coverage hole, decreasing transmission power, and enhancing transmission efficiency per bandwidth, and especially a system which makes use of relay nodes connected to a base station through optic cables as distributed antenna has a strong point in high-efficient resource allocation and cooperative signal transmissions between distributed antennas, since the system does not require additional radio resources for relaying and transmission/reception of control signals.
Meanwhile, since circuits processing a large number of subcarriers may be implemented on a single integrated circuit according to advances of semi-conductor technology, it has become possible to convert high-speed serial data into low-speed parallel data and transmit the converted low-speed parallel data. In addition, since computation has become more simplified according to adopting a Fast Fourier Transform (FFT) signal processing, an Orthogonal Frequency Division Multiplexing (OFDM) is being applied to various commercial wireless or mobile telecommunication systems.
Since a plurality of subcarriers are used in a wireless communication system using OFDM, signal can be transmitted using a property of flat channel even in a wireless environment having frequency selective fading channel. Through the above mentioned characteristic of OFDM, efficiency of bandwidth and data throughput may be enhanced, and modulation and coding scheme may be adapted to state of each of a plurality of channels. In addition, divided data resources may be multiplexed.
However, since OFDM uses characteristic of orthogonality between multiple subcarriers, it is very sensitive to frequency synchronization between subcarriers. Especially, in a wireless communication environment using a plurality of transmission points (or, nodes) such as a distributed antenna system and a cooperative transmission system, synchronization errors between subcarriers may cause significant performance degradation.
On the other hand, recently, an Alamouti coded OFDM, which obtains transmit antenna gains by using Alamouti codes in distributed antenna system, is being used. In the distributed antenna system, in order to maximize diversity gain, interferences due to frequency errors are required to be reduced.
As described above, studies for reducing inter-subcarrier interference in a wireless communication system using OFDM have progressed. However, since ongoing studies on reducing inter-subcarrier interference mainly have focused upon a wireless channel environment having flat fading property, there is a problem of performance degradation when they are applied to a frequency selective fading channel environment.